Memory Foam Mattress and Method of Construction

ABSTRACT

The present invention is directed toward an improved foam mattress. In one embodiment, the mattress has a base layer coupled to rectangular side sections each having a top surface. The top surfaces of the side sections extend above the top surface of the base layer and define a periphery of a space. The base layer and side sections are made of a material having a first resiliency. A central core layer is configured to fit entirely within the space defined by the side sections and is made of a material having a second resiliency, where the second resiliency is lower than said first resiliency. A top layer rests on the top surface of the central core layer and the top surface of the side sections. The top layer is made of a material of having a resiliency equal to or less than the second resiliency.

CROSS-REFERENCE

The present application relies on U.S. Patent Provisional Application No. 61/143,365, filed on Jan. 8, 2009, and incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of mattresses, and, more specifically, to a multi-layered foam mattress that allows for customization of the overall firmness, thickness and breathability of the mattress along with providing a uniform experience across the entire surface of the mattress.

BACKGROUND OF THE INVENTION

A conventional mattress generally includes a set of metal springs or coils mounted either on a base under a pad, or sandwiched in the center of a pair of pads. The metal springs and pad or pads are then covered with a strapping material. The entire structure is then sewn into a fabric cover and the edges are wrapped and sewn. Thus, once the mattress is fabricated, the components are not replaceable.

The limitations of metal spring mattresses combined with improved quality and durability of foam products has lead to the development of a foam core mattress as an alternative to metal spring mattress. A foam core mattress provides improved comfort and support compared with conventional spring-based mattresses. For example, spring-based mattresses inherently have varying feel properties over their surface, and it is quite difficult to perceivably remove or allay the variations of these feel properties relating to zone and surface areas.

A basic foam mattress may include one or more layers of foam having desirable properties and that are enveloped into a fabric cover. Typically, such a foam mattress may include a center core of relatively high resilience foam sandwiched between two layers of lower resilience foam encased in a fabric shell. This configuration allows for a reversible mattress. Typically, in prior art foam mattresses having multiple horizontal layers, the bottom layer comprising high resiliency foam is rigid and about 5-7 inches thick. On top of this layer are additional layers designed to provide the sleep comfort, such as egg crate foam and a viscoelastic layer. The viscoelastic layer provides softness to the mattress and is typically 3-5 inches thick. One of the major drawbacks of this design is that towards the edges of the mattress, the viscoelastic foam does not provide enough support. As a result, the user experiences a feeling of falling off the side of the bed.

Some prior art mattresses try to give more support around the edges by providing triangular wedges around the sides of the mattress. FIG. 1 illustrates an exemplary prior art mattress which includes 3″×3″ triangular wedges 101 at the sides. The problem with this design is that there is limited surface area to provide support on the top 103 of edges.

Since mattresses in this day are viewed highly personally, people look forward to enhanced comfort, especially with regard to firmness of the mattress. Consumers also demand better flexibility and the ability to customize the overall firmness, thickness and even feel of their mattress. Besides expecting enhanced durability of their mattress, people also look forward to breathability, specifically to the perceived temperature, which in case of luxury/costly layered-foam mattresses is highly desirable.

Accordingly, there is need in the prior art for an improved mattress that allows for better maneuverability of desired functional features of the mattress such as firmness, thickness, durability, provides uniform experience across the surface of the mattress, and provides for improved support at the mattress edges.

SUMMARY OF THE INVENTION

One embodiment of the present invention is directed toward a mattress comprising a base layer, having a top surface, coupled to a plurality of rectangular side sections each having a top surface, wherein the top surfaces of said side sections extend above the top surface of the base layer and define a periphery of a space and wherein said base layer and side sections are made of a material having a first resiliency; a central core layer, having a top surface, configured to fit entirely within the space defined by the side sections, said central core layer being made of a material having a second resiliency, wherein said second resiliency is lower than said first resiliency; and a top layer that rests on the top surface of the central core layer and the top surface of the side sections, said top layer being made of a material of having a resiliency equal to or less than the second resiliency.

The side sections provide support at the edges of the mattress. Optionally, the side sections are individual members bonded to said base layer. The side sections and said base layer are shaped from a single contiguous unit of material. The mattress further comprises an air foam layer placed between the top layer and the central core layer. The mattress further comprises an air foam layer placed between the central core layer and the base layer. The mattress is encased within at least one fire retardant fabric cover. The ILD for the material of the base layer and the side sections is in the range of 20 to 40, such as 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40. The ILD for the material of the central core layer and the top layer is in the range of 12 to 16, such as 12, 13, 14, 15, or 16. The material used for the base layer, side sections, central core layer and the top layer is a visco-elastic polyurethane foam. The overall thickness of the mattress is in the range of 7 to 13 inches.

In another embodiment, the mattress comprises a base layer, having a top surface, coupled to four rectangular side sections each having a top surface, wherein the top surfaces of said side sections extend above the top surface of the base layer and define a periphery of a space and wherein said base layer and side sections are made of a material having a first resiliency; a central core layer, having a top surface, configured to fit entirely within the space defined by the four side sections, said central core layer being made of a material having a second resiliency, wherein said second resiliency is lower than said first resiliency; and a top layer that rests on the top surface of the central core layer and the top surface of the side sections, said top layer being made of a material of having a resiliency equal to or less than the second resiliency. The thickness of each of said four side sections is in the range of 1 to 4 inches, and wherein the width of said side sections is in the range of 2 to 4 inches. The thickness and width of side sections at the foot and head of the mattress is less than that of the side sections at the sides of the mattress. The side sections are individual members bonded to said base layer. The side sections and said base layer are shaped from a single contiguous unit of material. The ILD for the material of the base layer and the side sections is in the range of 20 to 40. The ILD for the material of the central core layer and the top layer is in the range of 12 to 16. The material used for the base layer, side sections, central core layer and the top layer is visco-elastic polyurethane foam.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will be appreciated, as they become better understood by reference to the following Detailed Description when considered in connection with the accompanying drawings, wherein:

FIG. 1 illustrates an exemplary prior art mattress which includes triangular wedges at the sides;

FIG. 2 a is an illustration of a composite mattress structure, according to one embodiment of the present invention;

FIG. 2 b is an expanded view illustration of the composite mattress structure shown in FIG. 2 a;

FIG. 3 a shows a representative embodiment of the mattress structure shown in FIG. 2 a;

FIG. 3 b show a representative embodiment of the mattress structure shown in FIG. 2 b;

FIG. 4 illustrates another embodiment of the mattress structure;

FIG. 5 is a depiction of another embodiment of the composite mattress structure of the present invention;

FIG. 6 a is an illustration of one embodiment of the composite mattress structure;

FIG. 6 b is an illustration of another embodiment of the composite mattress structure; and

FIG. 6 c is an illustration of yet another embodiment of the composite mattress structure; and

FIG. 7 illustrates another embodiment of the composite mattress of the present invention with supportive edges on all the four sides.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment, the present invention is directed towards a composite mattress that allows for customization of its overall thickness and firmness.

In another embodiment, the present invention is directed towards a mattress having a uniform comfort level across the entire surface for allowing an individual to sit or sleep even at the edges without causing the mattress to deform or bend. The design of the mattress of present invention also prevents people from feeling as if they're going to fall off when sleeping on the edge of the bed.

In one embodiment, the present invention is directed towards a mattress comprising a base foam layer that further comprises a central base foam layer and two raised side sections, forming a T-shape structure; a central core foam layer that fits tightly within the channel created by the side sections over the base foam; and a topper foam layer that fully covers the top surfaces of the side sections and the central core foam.

In one embodiment of the mattress of the present invention, the density of the base foam layer is greater than the density of the core foam layer and topper foam layer. In addition, the densities of the core foam layer and topper foam layer can be varied and/or interchanged to customize the overall firmness of the mattress.

In one embodiment of the present invention, the base foam layer is firm and provides sturdy support to the topper layer, even along the edges, for a uniform feel across the surface of the mattress. The overall thickness of the mattresses is dependent on the thicknesses of the side sections and the topper foam layer along with any additional layer of foam that may optionally be added over the topper foam layer.

In another embodiment, the composite mattress of the present invention includes edge support on all the four sides.

In yet another embodiment, the present invention is directed towards a mattress that has better air permeability thereby allowing for better control of temperature of the mattress when an individual is using it. Thus, in one embodiment, the mattress of the present invention comprises a breathable air foam layer in addition to the base foam layer, the core foam layer, and the topper foam layer. In one embodiment the air foam layer is placed immediately underneath the topper foam layer and above the core foam layer, which in turn, is placed on top of the base foam layer. In another embodiment the air foam layer is sandwiched between the base foam layer and the core foam layer.

In another embodiment of the present invention, the mattress is wrapped with at least one fire retardant fabric cover.

Various modifications to the preferred embodiment, disclosed herein, will be readily apparent to those of ordinary skill in the art and the disclosure set forth herein may be applicable to other embodiments and applications without departing from the spirit and scope of the present invention and the claims hereto appended. Reference will now be made in detail to specific embodiments of the invention. Language used in this specification should not be interpreted as a general disavowal of any one specific embodiment or used to limit the claims beyond the meaning of the terms used therein.

FIGS. 2 a and 2 b illustrate one embodiment of the composite mattress structure 200 in accordance with an aspect of the present invention. Composite mattress 200 comprises base foam layer 204 and two longitudinally extending side foam sections 203. In addition, composite mattress further comprises a central foam core layer 210 that is received in the opening or space defined by side sections 203 and base foam layer 204; and foam topper layer 215 that rests on the top surface of central foam core layer 210 and side foam sections 203. In one embodiment, base foam layer 204 and raised side sections 203 are formed into a single unit of foam that has been shaped accordingly. In an alternate embodiment, base foam layer 204 and side foam layers 203 are fabricated as discrete components and assembled via bonding.

Referring now to both FIGS. 2 a and 2 b, the overall width 220 (X_(o)) and length 225 (L_(o)) of the composite mattress 200 is determined by the corresponding dimensions of industry standard beds that are commercially available, such as a king or queen-sized bed. However the width 220 and length 225 of the mattress 200 can also be customized.

In one embodiment, side sections 203 have widths of X_(s1) and X_(s2) respectively. In one embodiment X_(s1) is equal to X_(s2), however in an alternate embodiment X_(s1) is not equal to X_(s2). The width of base foam section 204 is determined as X_(b)=X₀−(X_(s1)+X_(s2)). The width X_(c) of foam core 210 is also equal to the width X_(b) of base foam 204, in one embodiment, such that core foam layer 210 fits squarely in the channel defined by side sections 203 and base foam 204. The width of foam topper layer 215 is equal to X_(o) which is the overall width of the composite mattress 200 so that the topper 215 fully covers the side sections 203 and the core foam layer 210.

The mattress of the present invention is advantageous in that the two side sections 203 provide support to the topper foam layer 215 along the edges allowing an individual to sleep, sit or rest on the edges of the mattress 200 without causing the mattress 200 to deform, bend or warp and thus giving the individual a uniform resting experience on the entire surface of the mattress 200. According to another aspect of the present invention, the width of the two side sections X_(s1), X_(s2) is chosen to optimize mattress support along the edges while maximizing the width X_(c) of the core foam 210 that defines the primary rest area for the individual.

Further, since the side sections for providing edge support are rectangular, it provides more top edge support than the triangular wedges used for edge support in prior art mattresses. This is because rectangular side sections have more surface area to provide better edge support.

The overall thickness 230 (T_(o)) of the mattress 200 is defined by the thickness T_(s) of the side sections 203 and that of the topper foam 215 denoted as T_(t). Thus, T_(o)=T_(s)+T_(t). In an alternate embodiment, the overall thickness T_(o) of the mattress 200 depends on the thickness T_(s) of the side sections 203, the thickness of the topper foam 215, denoted as T_(t), and the thickness T_(other) of any optional foam layer(s) placed over the topper foam layer 215. Thus, in this case T_(o)=T_(s)+T_(t)+T_(other). Also, the thickness T_(b) of the base foam 204 and T_(c) of the core 210 is such that T_(b) T_(c)=T_(s), that is, the sum of the thickness of the base 204 and core 210 is equal to the thickness of the side sections 203. In one embodiment T_(b) is equal to T. In another embodiment T_(b) is not equal to T_(c) where T_(b)>T_(c) or T_(c)>T_(b). However, in all embodiments the core 210 does not rise above the top edges of the side sections 203. The thickness T_(t) of the topper foam 215 may or may not be equal to those of the base 204 or the core 210.

In one embodiment, the various components of the composite mattress 200 are made of visco-elastic polyurethane foam, also referred to as memory foam or foam rubber. Viscoelastic foam is typified by its slow recovery after compression. Due to this property, viscoelastic foam can closely conform to the shape of the human body, and can efficiently distribute pressure over the whole surface. Viscoelastic foam also has ability to dampen vibration as well as absorb shock, absorbing up to 90% of impact. In addition to these key advantages, viscoelastic foam also reacts to body temperature and ambient temperatures, softening with heat and adjusting more easily to body contours. Due to its conforming aspect, viscoelastic material makes for a comfortable yet supportive mattress or mattress pad, and its low resilience works especially well in medical applications, for people with impaired mobility.

One of ordinary skill in the art would however appreciate that any material providing support and firmness characteristics similar to those provided by foam rubber can be used in the mattress of the present invention without exceeding the scope of the invention. Examples of alternate materials comprise latex foam, coir foam, XPS (Extruded Polystyrene) foam such as Styrofoam or Foamcore, or any other similar material known to persons of ordinary skill in the art.

In one embodiment of the mattress of the present invention, the thicknesses and densities of the side foam sections 203, base foam layer 204, core foam layer 210, topper foam layer 215 and therefore that of the overall composite mattress 200 are a function of at least the overall desired density of the composite mattress, desired therapeutic function of the mattress, age and weight of the individual who will be using the mattress and/or the climatic condition and therefore the place/region where the mattress will be used, and overall user preference.

Thus, in one embodiment the base foam structure 205 comprising of two longitudinally extending side foam sections 203 and the central base foam 204 is made of more dense and/or resilient (and firmer) foam material while the core foam layer 210 and the topper foam layer 215 are made of comparatively less dense and/or resilient (and thus softer) foam material. In addition, the core foam layer 210 is, in one embodiment, firmer and/or more resilient in comparison to the topper foam layer 215. This density and/or resiliency variation across sections of the composite mattress 200 is advantageous in that the softer upper layer(s), such as the topper foam layer 215, provides gentle support to the entire body while the firmer and/or more resilient core layer 210 provides greater support to a heavier area of the body that sinks deeper into the mattress 200. At the same time the substantially firmer and/or more resilient side sections 203 provide sturdy support to the core foam layer 210 and the topper foam layer 215. In an alternate embodiment while the core 210 and topper 215 have lesser densities and/or resiliency, in comparison to the base foam layer 204 and side sections 203, the densities and/or resiliencies of the core foam layer 210 and topper foam layer 215 may be same. In a yet another embodiment, the density and/or resiliency of the topper foam layer 215 is substantially higher than the core foam layer 210, which may be needed for therapeutic conditions of spondylitis or other similar conditions of the vertebrae for which a relatively harder/firmer bed is recommended.

One of the advantages of memory foam or visco-elastic polyurethane foam is that depending on its overall density and chemical additives it is firmer in cool temperatures and softer when warm. Higher density memory foam reacts to body heat which allows it to mould itself to the shape of a warm body within a short time period. Thus, the density of the mattress 200 and/or that of the topper foam layer 215 can be chosen depending upon the climatic condition and therefore the region of use of the mattress. In one embodiment, the density and/or resiliency of the topper foam layer 215 that is used in cold climatic conditions is slightly lower than that which is used in hot climatic conditions—though the topper foam layer 215 in either case may be of high or low density in absolute terms when viewed from industry standards or from therapeutic functionality. The reason for this relative density and/or resiliency difference, owing to climatic conditions, is that in cold climates memory foam is firmer with an anticipation that the body temperature of the user/individual would cause the foam to soften. However, in cold climates the body temperature of the user is likely to cause this softness of the foam over a longer period of time owing to the effect of external temperature. Thus, it will take a longer time for the foam to soften and provide the anticipated comfort to the user. On the other hand, in hot climates memory foam is softer and its interaction with body temperature of the user may further soften the foam to an undesirable effective density. Therefore, the topper foam layer 215 is of slightly high density when used in hot climatic conditions.

It may be noted that the weight and the visco-elasticity of the foam are determined by the amount of chemicals used in the composition of the polyurethane foam. Generally the higher the density, the greater the visco-elastic properties exhibited by the foam. The density does not determine the firmness of the foam. The industry standard that determines firmness of a visco elastic foam is known as Indentation Load Deflection (ILD). ILD rating is the number of pounds or weight required to achieve a 25% compression on a foam using a 50 square inch indentation. For example, foam with ILD rating 14 implies that it requires 14 lbs to acquire a 25% compression. ILD rating indicates how hard or soft the foam is—the higher the ILD rating, the harder the foam. ILD also determines how easily a foam will shape to the user's body and how much support it is capable of giving. Very low ILD foams are wonderfully cushy on the body, but provide very little support.

FIGS. 3 a and 3 b show one embodiment of the mattress of FIGS. 3 a, 3 b, denoted as 300, whereby the width of each side section 303 (X_(s1) and X_(s2)) is 2 inches. Also, in one embodiment, the thickness T_(b) of the base foam 304 is 4 inches, the thickness T_(c) of the core foam layer 310 is 2 inches and the thickness T_(t) of the topper foam layer 315 is 1 inch. Thus, the overall thickness T_(o) of mattress 300 is 7 inches. The base foam structure of mattress 300, formed from side foam sections 303 and base foam layer 304, is, in one embodiment, comprised of high density polyurethane foam. To provide adequate firmness and support, the ILD for the side foam sections 303 and base foam layer 304 is kept in the range of 20 to 40. In one embodiment, the high density polyurethane foam is of the order of 32 ILD. In one embodiment, the core foam layer and topper foam layer are of a comparatively lower density; for example, such layers may be comprised of 3.5 lb, pure visco foam, which provides adequate visco-elasticity without being uncomfortable to the sleeper. For the same purpose, ILD for the core and topper foam layers is kept in the range of 12 to 16. In an additional embodiment, the density rating of the visco foam is in the range of 2 lb to 6 lb. One of ordinary skill in the art would appreciate that firmness and support can be customized according to the user's preference, and materials of suitable density and ILD rating may be used accordingly.

In an alternate embodiment, as shown in FIG. 4, the overall thickness T_(o) of mattress 400 is 8 inches such that the thickness T_(b) of the base foam 404 is 5 inches, thickness T_(c) of the core foam layer 410 is 2 inches and thickness T_(t) of the topper foam layer 415 is 1 inch. Persons of ordinary skill in the art should note that the densities and thicknesses above are exemplary only and in no way are meant to be limiting to the invention.

FIG. 5 shows an embodiment of composite mattress structure 500 in accordance with another aspect of the present invention. Composite mattress 500 comprises base foam structure 505 formed from two longitudinally extending side foam sections 503 and a central base foam 504 deposited therebetween; foam core layer 510 that is received in the opening defined by side sections 503 and base foam 504; air barrier foam layer 514 that rests on the top surface of foam core layer 510, and foam topper layer 515 that rests on the top surface of air barrier foam layer 514 and side sections 503. While in one embodiment the base foam structure 505 is a single unit of foam that has been shaped to have the base 504 and two raised side sections 503; in an alternate embodiment the base foam structure 505 is fabricated by bonding together discrete pieces of base foam 504 and side foams 503.

The optional breathable air foam layer 514 allows for easier passage of air in and out of the mattress 500. This further allows the mattress 500 to better conform to a person's body and improves the deformation and recovery time of the foam as the person lies down, sits and/or moves on the mattress.

The overall width X_(o) and length (not depicted in FIG. 5) of the composite mattress 500 is determined by the corresponding dimensions of industry standard beds that are commercially available, such as a king or queen-sized bed. However the width and length of the mattress 500 can also be customized. The side sections 503 have widths of X_(s1) and X_(s2) respectively. In one embodiment X_(s1) is equal to X_(s2), however in an alternate embodiment X_(s1) is not equal to X_(s2). The width of base foam layer 504 is determined as X_(b)=X₀−(X_(s1)+X_(s2)). The widths X_(c) of foam core layer 510 and X_(a) of air barrier foam layer 514 are also equal to the width X_(b) of base foam layer 504 so that core foam layer 510 and air barrier foam layer 514 fit tightly in the channel defined by side sections 503 and base foam 504. The width of foam topper layer 515 is equal to X₀ which is the overall width of the composite mattress 500 so that the topper 515 fully covers the side sections 503, the core 510 and the air barrier foam 514.

The two side sections 503 provide support to the topper foam layer 515 along the edges allowing an individual to sleep, sit or rest on the edges of the mattress 500 without causing the mattress 500 to deform, bend or warp thereby giving the individual a uniform resting experience on the entire surface of mattress 500. In one embodiment the width of the two side sections X_(s1), X_(s2) is chosen to optimize mattress support along the edges while maximizing the widths X_(c) and X_(a) of the core foam layer 110 and air barrier foam layer 514, respectively, that define the primary rest area for the individual.

In one embodiment, the overall thickness T_(o) of the mattress 500 depends on the thickness T_(s) of the side sections 503 and that of the topper foam layer 515 denoted as T_(t). Thus, T_(o)=T_(s)+T_(t). Also, the thickness T_(b) of the base foam layer 504, T_(c) of the core foam layer 110 and T_(a) of air barrier foam layer 514 is such that T_(b)+T_(c)+T_(a)=T_(s), that is, the sum of the thickness of the base 504, core foam layer 110 and air barrier foam layer 514 is equal to the thickness of the side sections 503. In one embodiment T_(b) is equal to T_(c). In another embodiment T_(b) is not equal to T_(c) where T_(b)>T_(c) or T_(c)>T_(b). In one embodiment the thickness T_(a) of air barrier foam layer 514 is substantially less than the thicknesses T_(b) or T_(c) of the base and core foam layers. In another embodiment, the thickness T_(a) is equal to either T_(b) or T_(c). In yet another embodiment, the thickness T_(a) is greater than T_(b) or T_(c). However, in all embodiments the air barrier foam layer 514 does not rise above the top edges of the side sections 503. The thickness T_(t) of the topper foam layer 515 may or may not be equal to those of the base 504, the core foam layer 510 or the air barrier foam layer 514.

In one embodiment, the air barrier foam layer 514 is made of poly foam that acts as a breathable air layer while other components of the composite mattress 500 are made of visco-elastic polyurethane foam, also referred to as memory foam or foam rubber. However, any material providing support and firmness characteristics similar to those provided by foam rubber can be used without exceeding the scope of the invention. Examples of alternate materials comprise latex foam, coir foam, XPS (Extruded Polystyrene) foam such as Styrofoam or Foamcore, or any other similar material known to persons of ordinary skill in the art.

FIG. 6 a shows one embodiment of the mattress 500 of FIG. 5, denoted herein as 600. As shown in FIG. 6 a the width of each of the side sections 603 X_(s1) and X_(s2) is 3 inches. Also, in this particular embodiment, the thickness T_(b) of the base foam layer 604 is 6 inches, the thickness T_(c) of the core foam layer 610 is 2 inches, the thickness T_(a) of the air barrier foam layer 614 is ⅜ inches and thickness T_(t) of the topper foam layer 615 is 1 and ⅝ inches. Thus, the overall thickness T_(o) of mattress 600 is 10 inches.

While in one embodiment, as shown in FIG. 6 a, the air barrier foam 614 is positioned as the layer immediately underneath the topper foam layer 615, in an alternate embodiment, the air barrier foam 614 is sandwiched as a layer between the base foam layer 604 and the foam core layer 610, as shown in FIG. 6 b.

In one embodiment, side foam sections 603 and base foam layer 604 of mattress 600 are comprised of high density polyurethane foam. To provide adequate firmness and support, the ILD for the side foam sections 603 and base foam layer 604 is kept in the range of 20 to 40. In one embodiment, the high density polyurethane foam is of the order of 32 ILD. In one embodiment, the high density polyurethane foam is on the order of 32 ILD. In one embodiment, core foam layer 610 and topper foam layer 615 are comprised of a foam of a relatively lower density than the side sections 603 and base foam layer 604, such as 5 lb pure visco foam, which provides significant visco-elasticity. For the same purpose, ILD for the core and topper foam layers is kept in the range of 12 to 16. In an additional embodiment, the density rating of the visco foam is in the range of 2 lb to 6 lb.

Persons of ordinary skill in the art should note that the densities and thicknesses above are exemplary only and in no way are meant to be limiting to the invention. For example as shown in FIG. 6 c, in an embodiment, the overall thickness T_(o) of the mattress 600 depends on the thickness T_(s) of the side sections 603, the thickness of the topper foam layer 615 denoted as T_(t) and the thickness T_(other), which represents an optional foam layer(s) 620 placed over the topper foam layer 615. Thus, in this case T_(o)=T_(s)+T_(t)+T_(other). Thus, in one embodiment, the overall thickness T_(o) of mattress 600, in this case, is 13 inches. Also, for example, while side foam sections 603 and base foam layer 604 are comprised of a high density polyurethane foam, core foam layer 610 and topper foam layer 615 are of a comparatively lower density. Thus, in one embodiment, side foam sections 603 and base foam layer 604 are comprised polyurethane foam having an ILD range of 20-40, while core foam layer 610 and topper foam layer 615 are comprised of pure visco foam of 5 lb density. Further, the additional topmost layer 620 may be comprised of a foam having the relatively lowest density, such as 3 lb.

It should be appreciated that, in any of the aforementioned embodiments, side sections 603 can be placed at each of the four sides of the mattress, including the right, left, head, and foot sides. In such a case, the core foam layer 610 is adjusted in size to be accommodated in the space created by the four side sections.

FIG. 7 illustrates yet another embodiment of the mattress of the present invention. Referring to FIG. 7, mattress 700 includes not only side rails 701 and 702, which are made up of a high resiliency material such as polyurethane foam, but also includes rails 703 and 704 at the head and foot of the mattress as well. This configuration provides enough support at all the four edges of the bed. The four edge rails are supported by a high resiliency base foam structure (not shown), which forms the base of the mattress in a manner similar to that described earlier with reference to embodiments shown in FIGS. 3 a, 3 b, 5 and 6 a. Further, the four edge rails can be discrete pieces in one embodiment that are bonded to a support base. In another embodiment, a single unit of foam is shaped to have a base and four raised edge sections that form the edge rails.

At the centre of the space created by the four high resiliency edge rails 701, 702, 703 and 704, and on the top of the support base of the mattress, is a core foam layer 705 comprising material of relatively lower resiliency, such as pure viscoelastic foam. As in previous embodiments, a foam topper layer (not shown), also made up of a low resiliency material such as pure viscoelastic foam rests on the top surface of central foam core layer 705 and edge foam sections 701, 702, 703 and 704.

Thus, the base foam structure along with the edge sections are made of more dense (and rigid) and/or more resilient foam material while the core foam layer and the topper foam layer are made of comparatively less dense and/or less resilient (and thus softer) foam material. In addition, the core foam layer is, in one embodiment, firmer in comparison to the topper foam layer. This density variation across sections of the composite mattress 700 is advantageous in that the softer upper layer(s) provide gentle support to the entire body while the firmer bottom layer(s) provides greater support to a heavier area of the body that sinks deeper into the mattress. At the same time the substantially firmer edge rails not only help prevent the feeling of falling off the edge of the bed while sleeping on the sides, but also provide sturdy support to the core foam layer and the topper foam layer.

In one embodiment, the density of the material comprising the head rail 703 is relatively higher than that of the material comprising foot rail 704. This configuration is useful in therapeutic conditions where better support is required for the head and neck.

In the embodiment of FIG. 7, the thickness of the rigid edge rails is designed to optimize comfort and support. Since thinner rails provide inadequate support and too thick rails make the mattress uncomfortable to sleep, therefore in one embodiment, the thickness of edge rails is designed to be in the range of 1 to 6 inches, optimally 2-3 inches. Further, the thickness of edge rails can be customized according to the requirement and user preference. In one embodiment for example, the rails at the foot and head of the mattress are less thick than at the sides.

Optionally, covers may be used to envelope the mattress of the present invention. Referring back to FIG. 2 a, 2 b, in one embodiment, the base foam structure comprising side foam sections 203 and base foam layer 204, along with the central foam core layer 210 are wrapped using a first cover (not shown) and the topper foam layer 215 is wrapped using a second cover (not shown). In another embodiment, a first cover (not shown) is used to wrap side foam sections 203 and base foam layer 204, a second cover (not shown) is used to wrap the central core foam layer 210 and a third cover (not shown) is used for the topper foam layer 215.

Referring now to FIG. 5, in one embodiment, the base foam structure 505, comprising the side foam sections 503 and base foam 504, along with the foam core 510 and the air barrier foam 514 are wrapped using a first cover (not shown) and the topper foam layer 515 is wrapped using a second cover (not shown). In another embodiment, a first cover (not shown) is used to wrap the base foam structure 505, a second cover (not shown) is used to wrap the core foam 510, a third cover (not shown) is used for the air barrier foam 514 and a fourth cover (not shown) is used for the topper foam layer 515.

For convenience of easy removal/changing the covers have zippers, as is known in the art. The covers can be made of cotton, which is breathable, absorbent and washable, or other permeable or impermeable fabric such as wool, silk, linen, polyester fleece. In one embodiment, the covers are fire retardant. For example, flame-resistant covering may be made of cotton, linen, wool, silk, nylon, an acrylic or other synthetic fabric that is impregnated with a fire retardant compound such as, but not limited to, boric acid (H₃BO₃), zinc borate, antimony trioxide (Sb₂O₃), vinylidene chloride, decabromodiphenyl oxide (DBDPO or Deca), Melamine or PVDC. Alternatively, flame-resistant covering is made of a flame-retardant fabric such as, but not limited to, a fabric made of para-aramid fibers.

The above examples are merely illustrative, and although only a few embodiments of the present invention have been described herein, it should be understood that the present invention might be embodied in many other specific forms without departing from the spirit or scope of the invention. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention may be modified within the scope of the appended claims. 

1. A mattress comprising: a base layer, having a top surface, coupled to a plurality of rectangular side sections each having a top surface, wherein the top surfaces of said side sections extend above the top surface of the base layer and define a periphery of a space and wherein said base layer and side sections are made of a material having a first resiliency; a central core layer, having a top surface, configured to fit entirely within the space defined by the side sections, said central core layer being made of a material having a second resiliency, wherein said second resiliency is lower than said first resiliency; and a top layer that rests on the top surface of the central core layer and the top surface of the side sections, said top layer being made of a material of having a resiliency equal to or less than the second resiliency.
 2. The mattress of claim 1, wherein the side sections provide support at the edges of the mattress.
 3. The mattress of claim 1, wherein said side sections are individual members bonded to said base layer.
 4. The mattress of claim 1, wherein the side sections and said base layer are shaped from a single contiguous unit of material.
 5. The mattress of claim 1 further comprising an air foam layer placed between the top layer and the central core layer.
 6. The mattress of claim 1 further comprising an air foam layer placed between the central core layer and the base layer.
 7. The mattress of claim 1, wherein the mattress is encased with at least one fire retardant fabric cover.
 8. The mattress of claim 1, wherein the ILD for the material of the base layer and the side sections is in the range of 20 to
 40. 9. The mattress of claim 1, wherein the ILD for the material of the central core layer and the top layer is in the range of 12 to
 16. 10. The mattress of claim 1, wherein the material used for the base layer, side sections, central core layer and the top layer is a visco-elastic polyurethane foam.
 11. The mattress of claim 1, wherein the overall thickness of the mattress is in the range of 7 to 13 inches.
 12. A mattress comprising: a base layer, having a top surface, coupled to four rectangular side sections each having a top surface, wherein the top surfaces of said side sections extend above the top surface of the base layer and define a periphery of a space and wherein said base layer and side sections are made of a material having a first resiliency; a central core layer, having a top surface, configured to fit entirely within the space defined by the four side sections, said central core layer being made of a material having a second resiliency, wherein said second resiliency is lower than said first resiliency; and a top layer that rests on the top surface of the central core layer and the top surface of the side sections, said top layer being made of a material of having a resiliency equal to or less than the second resiliency.
 13. The mattress of claim 12, wherein the thickness of each of said four side sections is in the range of 1 to 4 inches, and wherein the width of said side sections is in the range of 2 to 4 inches.
 14. The mattress of claim 12, wherein the thickness and width of side sections at the foot and head of the mattress is less than that of the side sections at the sides of the mattress.
 15. The mattress of claim 12, wherein said side sections are individual members bonded to said base layer.
 16. The mattress of claim 12, wherein the side sections and said base layer are shaped from a single contiguous unit of material.
 17. The mattress of claim 12, wherein the ILD for the material of the base layer and the side sections is in the range of 20 to
 40. 18. The mattress of claim 12, wherein the ILD for the material of the central core layer and the top layer is in the range of 12 to
 16. 19. The mattress of claim 12, wherein the material used for the base layer, side sections, central core layer and the top layer is visco-elastic polyurethane foam. 